Federal safety investigators revealed Wednesday that crew members aboard two Coast Guard boats involved in collisions in California and South Carolina last year were using wireless devices for conversation or text messaging unrelated to vessel operations. The collisions killed one person and injured 10.

The NTSB said in a statement that it has not determined the probable causes of the collisions in San Diego Bay and the Charleston, S.C., harbor, but was urging the Guard to develop a thorough policy on use of the devices by the service and to issue a safety advisory to the maritime industry.

The National Transportation Safety Board did not say how many members of each crew were using the devices or what their roles were on the boats, but said the accidents raise concerns about the potential for distraction.

It noted in a letter to the Guard that the service considers all crew members to be lookouts when a vessel is under way.

The Coast Guard issued a policy on July 16 that prohibits use of the devices by the boat operator — the person at the wheel and throttles — at all times while under way, said Lt. Cmdr. Chris O'Neil, chief of media relations at Guard headquarters in Washington, D.C.

The policy prohibits other crew members from using the devices unless expressly approved by the boat operator, known as the coxswain, O'Neil said.

A copy of the Coast Guard's policy provided to The Associated Press shows it is essentially a three-paragraph statement with two sentences of orders to crews.

O'Neil defended the existing rule as very specific on the use of the electronic devices. That policy does not define the purposes or situations in which use can be authorized.

"It allows the coxswain to exercise judgment ... to determine whether it is prudent to allow use of that device," O'Neil said.

The NTSB said the Guard must identify specific risks associated with distraction while using the devices and address them in the policy. It said that policy was only a "first step" in safety improvements recommended for the Guard.

O'Neil could not comment on details of the two accidents, citing ongoing investigations.

The first accident cited by the NTSB occurred on Dec. 5 at Charleston as two Coast Guard boats, each with a crew of three, were returning to base after escorting a cargo ship. One of the boats collided with the Thriller 09, a small vessel that was carrying 22 passengers on a tour of Christmas light displays, injuring five passengers and a sixth who sought treatment later.

The second involved a Coast Guard boat with a crew of five colliding with a 24-foot pleasure boat during San Diego Bay's Parade of Lights on Dec. 20. Of the 13 people aboard the civilian boat, an 8-year-old boy was killed and four others were seriously injured. No Coast Guard personnel were injured.

In the San Diego incident, four petty officers are facing Coast Guard charges ranging from involuntary manslaughter to negligent homicide and dereliction of duty. A Coast Guard district commander will decide whether they face a court-martial.

The family of the dead child, Anthony Cole DeWeese, has sued the federal government for unspecified damages. A message for the family's attorney was left Wednesday by The Associated Press.

The hazardous use of cell phones was also the focus of a probe into the 2008 collision of a commuter train and a freight train that killed 25 people in Los Angeles. Investigators believe the commuter train engineer ran a red light seconds after he was text messaging.