Houston police said two people were killed and one employee is unaccounted for after a huge building explosion in northwest Houston early Friday, authorities said. The blast damaged over 200 homes, leveling entire nearby structures and smashing in windows and doors throughout the neighborhood. The Houston Chronicle reported the blast occurred at 4:20 a.m. CT at Watson Valve Services, a machining and manufacturing company, and that the chemical propylene is being emitted from the site and will dissipate. Houston Fire Chief Sam Peña said Friday at least one person has also been hospitalized on account of the blast, and at least 18 people have reported minor injuries.

Reporters who were as far as 10 miles from the scene said they could feel the blast, and social media platforms are full of early-morning posts by Houstonians with broken glass and home damage. Police Chief Art Acevedo told the NBC outlet that the family of a missing employee is at the scene, but it cannot be properly searched because of the dangerous conditions inside. Authorities warned of additional explosions and to avoid exposure to the air around the site. It has not been established what caused the explosion, but the Houston Fire Department told reporters it involved liquid nitrogen, which is leaking at the scene. An unverified video purported to be of the explosion was posted on social media.