Ride the Ducks, a company offering land/sea sightseeing tours by amphibious vehicle in six locations in the U.S., has suspended tours at all locations following a “duck boat”-barge crash on the Delaware River in Philadelphia on Wednesday.

A message on its website said, “Our thoughts and prayers are with our Philadelphia tour guests, crew members and their families. We are attending to their needs first. In the interim, we have voluntarily suspended our Ride the Ducks operations nationwide. If you already have a reservation, you can receive a full refund or reschedule for a future date. We will resume operations shortly.” 

Ride the Ducks, based in Norcross, Ga., also operates amphibious vehicle tours in Branson, Mo.; Newport, Ky.; Stone Mountain Park, Ga.; San Francisco; and Seattle.

According to a CNN report, members of the National Transportation Safety Board are in Philadelphia to investigate the cause of the crash, which left two people unaccounted for and sent at least 10 to the hospital for treatment. Search efforts for the missing people, a 16-year-old female and a 20-year-old male, resumed Thursday morning.

The boat had been carrying 37 people, including two crew, when it developed “mechanical trouble” and stalled before a barge pulled by a tugboat hit it, causing it to sink.