This story has been updated.

An underground structure exposed after an explosion Friday night that killed four people at a commercial property on the Southeast Side filled with rainwater over the weekend, slowing the investigation into the cause of the blast.

The San Antonio Fire Department’s arson bureau is leading the investigation, fire officials said Monday, and is working with the FBI, the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) and the San Antonio Police Department.

The cause of the explosion, which occurred at around 11:30 p.m. Friday night at K-Bar Services, a road construction company located in the 9700 block of South Presa Street, is still unknown. 

When fire crews arrived at the scene, it was “pitch black,” said fire department spokesman Joe Arrington. One body was found that night. When daylight arrived, crews could see an underground structure exposed by the blast, and two more bodies were discovered. A fourth body was discovered Sunday, Arrington said.

Investigators believe only four people were at the scene at the time of the explosion, Arrington said, but no scenarios have been ruled out. Police and fire crews remained at the scene Monday. The property is fenced off, and the aftermath of the explosion cannot be seen from the road.

The Bexar County Medical Examiner’s Office on Saturday identified 36-year-old Roger Huron Jr. as a person who died in the explosion.

The other victims have not yet been identified, but include a 57-year-old white male, a 61-year-old white male and a 28-year-old white female, according to the medical examiner’s office.

Rain over the weekend hampered the investigation, as the crater caused by the explosion filled with water, Arrington said. Crews have since pumped the water out.

K-Bar Services has been in business since 1986, according to the Better Business Bureau. The company’s website appeared to be down Monday morning.

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Raquel Torres

Raquel Torres is the San Antonio Report's breaking news reporter. She previously worked at the Tyler Morning Telegraph and is a 2020 graduate of Stephen F. Austin State University.