STERLING, Va. (AP) _ Four people remained hospitalized today after a chemical explosion in a computer parts manufacturing plant sprayed caustic materials throughout the plant, officials said.

Sixteen people were injured in the blast Monday morning at the Automata Inc. plant, authorities said.

By Monday night, two remained in critical condition, two in serious condition, said Bill Goldfeder, director of the Loudoun County Fire and Rescue Department. The others injured in the explosion at the Automata, Inc. computer parts factory were treated at local hospitals and released, he said.

The blast spewed a chemical containing sulfuric acid and hydrochloric acid into the plant.

''We had people get doused and drenched with the chemical when it exploded,'' said fire chief Jim Kiser, head of the department's emergency response team. Kiser said people continued to breathe chemical fumes as they were being treated.

The explosion happened in the processing room of the plant shortly before 7 a.m. EDT, when a machine used in making electronic circuit boards for computers blew up, authorities said.

Goldfeder said investigators had ruled out foul play as the cause. The incident will probably be ruled an industrial accident ''due to human error or equipment failure,'' he said.

Workers, who were apparently changing the chemical mixture that's used to clean copper parts, suffered a variety of injuries.

''Our units found several people outside suffering from everything from respiratory to shrapnel-type injuries from the explosions, metal parts and what have you,'' Goldfeder said.

In addition to plant employees, the victims included three firefighters and a Loudoun County Sheriff's Department deputy.

''Hydrochloric acid and sulfuric acid were involved,'' said Goldfeder. ''They're bad. They both cause injuries to the skin as well as respiratory problems.''

The blast created no toxic cloud and presented no danger to the environment or to people living near the plant, authorities said.

The plant employs about 125 people.