An explosion occurred at a resort in Hagtana, Guam Thursday, leaving at least one person injured, according to local reports. Although visitors were initially evacuated as a precaution, the hotel reopened a few hours later.

The investigation as to what happened continues.

Guam Hotel Explosion

Caution tape cordons off the entrance to a bar at the Hilton Guam Resort & Spa in Hagatna, Guam, Friday, Sept. 27, 2013. An explosion at the resort on Thursday night hurt two people and led to a four-hour evacuation of about 650 guests. (Photo: AP/Grace Garces Bordallo)

The Pacific Daily News reported that the blast hit near the Hilton Guam Resort & Spa’s koi pond outside the hotel’s outdoor Tree Bar.

Officials said they could only confirm one injured person was received to the hospital, but the Guam Fire Department said three people have been treated with injuries.

Although the cause of the blast is not yet known, FBI and Homeland Security officials are on scene at the resort as it is being investigated.

Calls about the explosion started coming in to officials at 8:40 pm local time.

This is a developing story.