At least four people were killed and two others injured when a house exploded on Thursday night in a borough about 40 miles north of Philadelphia, the authorities said.

Police and fire officials in Pottstown, Pa., were dispatched to the site just after 8 p.m., Justin M. Keller, a local official, told reporters during a news conference. They found “multiple victims needing medical care,” he said.

Besides the four confirmed fatalities, two people were hospitalized and two others may be unaccounted for, Mr. Keller said. An investigation was underway, he added, and multiple agencies, including the Pennsylvania State Police and the Red Cross, sent personnel to the site late Thursday night.

Information about the cause of the explosion and the identities of those killed or injured was not available as of early Friday. The Pottstown Police Department could not immediately be reached for comment.

Stephen J. Rodriguez, the superintendent of the Pottstown School District, said in a message to parents on Thursday night that classes would be canceled on Friday because of the explosion.