NEWBURYPORT - A series of explosions blew a hole in the roof and forced the evacuation of a pharmaceutical chemical company at the city's industrial park this morning, but no one was injured, the city's deputy fire chief said.

The explosions inside PCI Synthesis forced the evacuation of several buildings near the Opportunity Way complex.

Newburyport Fire Department Deputy Chief Stephen Bradbury said when firefighters responded to an alarm around 4:30 a.m. they saw smoke inside the company's manufacturing plant.

While firefighters were investigating the smoke, three explosions occurred in a different room. 

"(Firefighters) evacuated immediately," Bradbury said. 

Once firefighters left the building, another three explosions occurred, ripping a  5-by-8-foot hole in the roof. 

A state hazardous materials team was called to the scene, and three adjacent businesses were evacuated.

The cause of the explosion is still under investigation.

A robot is expected to be placed into the area where the explosions took place to determine whether it is safe for firefighters and others to reenter the affected space. 

According to the PCI Synthesis website, the drug substance manufacturer has a 75,000 square foot facility that is equipped with 22 reactors providing more than 20,000 gallons of total capacity. 

In 2015, federal safety officials fined the company for a violation involving 23 people. It was classified as "serious" by the Occupational Safety and Health Administration.

The company also has a research and development facility at Devens, the former military base straddling the towns of Ayer and Harvard.