Seven people, including four police officers, were injured during an explosion at a Baltimore County nail salon on Monday night.

Baltimore County Police responded to an explosion at Libra Nails and Spa located in a strip mall in Milford Mill, Md. In addition to the four cops, two emergency medical service providers and one civilian were also injured from the blast.

The fire was started by a man in emotional distress known to the staff of Libra Nails and Spa, Baltimore County Police told The Post. The explosion occurred after the man ran into the back of the salon. The Bureau of Alcohol, Tobacco, and Firearms will help determine how the explosion was set off.

Fire officials told the Baltimore Sun that the man was a former employee of the salon.

The suspect suffered serious injuries and was taken immediately to Johns Hopkins Bayview. The first responders were also hospitalized but did not sustain life-threatening injuries, police confirmed.

The fire was upgraded to a HAZMAT situation by fire officials due to the presence of chemicals in substances like nail polish remover. Officials said the fire was under control by 10:30 p.m.

Milford Mill is an unincorporated town of about 30,000 people 12.5 miles outside of Baltimore.