HOUSTON -- A fire broke out at a southeast Houston environmental waste company plant while federal officials were raiding the facility, leading to a shelter-in-place for neighboring residents, KPRC Local 2 reported Tuesday.

The blaze broke out in the back of an 18-wheeler at CES Environmental Inc. on Griggs Road near Carol Lane shortly before 4 p.m.

An evacuation order was not issued, but residents within a 1/4 mile of the facility were asked to shelter-in-place as a precaution for a couple of hours. The shelter-in-place was lifted shortly before 6 p.m.

The fire was contained to the truck.

Firefighters let the unknown chemical burn itself out. Officials said the substance appeared to spontaneously combust.

No injuries were reported.

Officers with the U.S. Attorney's Office and the Environmental Protection Agency raided two CES facilities on Tuesday where three workers have died in the last six months.

Davilyn Walston, spokeswoman for the U.S. Attorney's office, said the Houston and Port Arthur facilities of CES Environmental Inc. were searched Tuesday.

Walston declined to provide any more details.

"To protect the integrity of the investigation, (we) cannot go into any detail," she said.

A Houston Police Department command unit was at the southeast Houston plant and began serving warrants at the plant at 7 a.m.

"There's some complicated issues here. As you know, there's been some safety issues in the past. And we've had to slow down because of some safety issues in the facility," said Stephen Dicker with HPD's environmental division.

CES transports and disposes of organic waste. It issued a statement Tuesday that said it was given no explanation of the raid from federal authorities but its officials are cooperating.

The CES statement said its officials are saddened by the July incident that killed an employee cleaning a tanker truck, but it is under internal investigation.

Port Arthur Justice of the Peace Tom Gillam said he began investigating the Port Arthur site of CES after a worker died from inhaling hydrogen sulfide, a gas produced by human and animal waste. Gillam said he alerted federal authorities after he discovered that hydrogen sulfide contributed to two of the three deaths.

Bruce Howard, 45, was killed during a fire at the Griggs Road plant last month. The company said Howard had worked at the plant for about 18 months.

Investigators would not say if the search was related to the deaths.

Neighbors who live nearby have demanded the plant be shut down. Residents said CES has a long list of safety concerns, including poor air.

Neighbors said it is affecting their health.

"It's migraines. I just woke up from lying down with one, "neighbor Yyoulanda Fischer said.

"The smell gets bad. It smells like old, old rotten eggs and oil mixed. It makes my stomach hurt," Jacquez Fischer said.

Shelter-In-Place Order

When a shelter-in-place is issued, residents should:

Go inside.
Shut all doors and windows.
Turn off air conditioners and heaters to prevent outside air from getting inside.
Stay off the phone.
Do not use fireplaces. Put out fires and close all dampers.
Move to a room with the fewest windows and doors. Tape around doors, windows, exhaust fans and vents using plastic sheeting or garbage bags, if directed.
Turn on the radio or television to listen for further instructions.

Families are advised to have the following items in a shelter-in-place kit:

Two rolls of duct tape
Cloth and paper towels
Plastic sheets or trash bags
Flashlight and extra batteries
Battery-powered radio
Two gallons of water
Nonperishable foods