Hot-Air Balloon Crash in Arizona Kills 4

Four people were killed and one person was critically injured after a hot air balloon crashed in a desert area about 50 miles northwest of Tucson, Ariz., on Sunday morning, the police said.

The crash happened around 7:50 a.m. in Eloy, Ariz., the Eloy Police Department said on Facebook.

The cause of the crash remained under investigation, the police said, adding that they were working with the National Transportation Safety Board and the Federal Aviation Administration to determine a cause.

The N.T.S.B. said on social media that it was investigating the crash but offered no further details.

The police said they were withholding the names of the victims pending notification of next of kin. The identity of the operator of the hot air balloon, the place it took off from and its destination were also unavailable.

The police did not respond to requests for additional information.

“While we continue our efforts, we ask for your thoughts and support for the families and loved ones affected during this difficult time,” the police said on Facebook.