The Texas fertilizer plant that exploded last week killing 14 people last had a full safety inspection almost 30 years ago.
The United States Department of Labor website said the Occupational Safety and Health Administration (OSHA) visited West Chemical and Fertilizer Company in February 1985.
The revelation comes amid growing concern about how health and safety rules were followed at the plant, which supplied agricultural chemicals and fertilizer to area farmers.
West Chemical and Fertilizer Plant, that exploded on Wednesday killing 14 and injuring 200, was last inspected by the Occupational Safety and Health Administration in 1985
The explosion destroyed this apartment complex as well as damaged schools and a nursing home
Workers are pictured among the debris of the plant. The cause of the explosion has still not been determined
Volunteer firefighters and paramedics were among 14 people who died on Wednesday when the blast flattened the fertilizer plant.
Two hundred people were also injured in the explosion that destroyed a 50-unit apartment block, about 50 houses and damaged several schools and a nursing home.
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The cause of the explosion has not yet been determined, although the facility stored liquid anhydrous ammonia fertilizer in huge tanks and ammonium nitrate in dry form.
Both are considered hazardous materials that could ignite under certain conditions.
Records reviewed by The Associated Press show that in OSHA last inspected the West Chemical & Fertilizer Co., as it was known at the time, in 1985.
It then fined the company $30 for a serious violation for storage of anhydrous ammonia.
OSHA cited the plant for four other serious violations of respiratory protection standards but did not issue fines. The maximum fine for a serious violation was $1,000.
The agency has jurisdiction over more than 7million workplaces but it is not uncommon for some companies to go years without inspection.
Reviews into the plant's documentation also found that last year it was storing 1,350 times the amount of ammonium nitrate that would normally trigger safety oversight by the U.S. Department of Homeland Security.
However, a source close to the agency told Reuters that company owners did not tell them about the high levels of the dangerous substance.
270 tons of ammonium nitrate - the same substance used by the Oklahoma bomber - was stored at the plant last year
Investigators are still probing the cause of the explosion as workers began to clear debris on Monday
Volunteers sort through goods donated for victims the explosion that has devastated the small community
Ammonium nitrate, which can be used in bomb making, is supposed to be tightly monitored.
Yet, documents filed to the Texas Department of State Health Services that showed the plant stored 270 tons of the substance were not shared with the agency.
Timothy McVeigh used two tons of ammonium nitrate in a truck bomb in Oklahoma City in 1995, killing 168 people and injuring more than 800.
Rep. Bennie Thompson, a ranking member of the House Committee on Homeland Security, said: 'It seems this manufacturer was willfully off the grid.
'This facility was known to have chemicals well above the threshold amount to be regulated under the Chemical Facility Anti-Terrorism Standards Act (CFATS), yet we understand that DHS did not even know the plant existed until it blew up.'
Partial safety inspections of the fertilizer plant had been held since 1985 and in 2011 the company owners filed an emergency response plan stating there was 'no' risk of fire or explosion at the facility, according to the Huffington Post.
The U.S. Department of Transportation Pipeline and Hazardous Materials Safety Commission fined West Fertilizer plant owners $5,200 during a partial inspection in 2011.
One of the violations was 'failing to develop and adhere to a security plan' for the transportation of large amounts of anhydrous ammonia.
Last week, plant owner Donald Adair released a statement saying that 'out of respect for the investigative process' he and other bosses would restrict their public comments.
Local media have not been able to contact him or manager Ted Uptmore in recent days.
Churchgoers huddle to pray after a service for the First Baptist Church in a field on Sunday
Homes and cars were destroyed by the blast and some residents say they are frustrated they have not been able to return to their properties to check on the damage
Yesterday, the sole school that was not damaged in the deadly blast reopened.
It is the only one of four schools in the small town that remained intact.
'It's the first step, but getting back going again, some normalcy for our staff and faculty's lives and our kids' lives, it's a huge milestone,' said Marty Crawford, West Independent School District Superintendent.
Over the weekend, volunteers built three temporary classrooms at the elementary school.
Some residents said they are frustrated that they have not been allowed back to their homes to check on the damage.
Bill Killough, 76, said he had checkbooks, medication and guns sitting out where he had left them after fleeing his home in a hurry.
'They don't care. Don't care. There's no reason why they [federal authorities' can't escort residents in to get their belongings', he said.
President Barack Obama plans to attend a memorial service on Thursday for victims of the fertilizer plant explosion.
This aerial shot shows the remains of the fertilizer plant
Part of the nursing home that was destroyed in the explosion
High school students hug as they arrive for classes at a temporary facility in nearby Waco