Four unauthorized modifications caused a mast aboard a sailing catamaran to snap and hit a 13-year-old boy in the head, killing him, in a 2006 incident, according to findings of a Coast Guard investigation released today.

The Coast Guard also said today that an investigation into a separate incident in 2007, when a 48-year-old man was killed when the mast on a catamaran snapped and hit him, was caused by a small crack on the "base of the step" that holds the mast.

The two incidents were investigated together so that the Coast Guard could determine whether it should beef up its standards for inspecting sailing catamarans. In the wake of the two deaths, the Coast Guard said it has done just that, making changes to inspection standards that could be adopted nationally.

The two deaths occurred less than four months apart about two years ago in Hawaii waters. On Dec. 1, 2006, a 13-year-old boy was killed aboard the Na Hoku II off Diamond Head. A 48-year-old man was killed aboard the Kiele V off Kaanapali, Maui on March 25, 2007.

Coast Guard officials said yesterday that in addition to the unauthorized modifications on the Na Hoku II, two of the catamaran's crew members — the master and a crew member — tested positive for marijuana immediately after the incident.

U.S. Coast Guard Capt. Barry Compagnoni said the master and the company could face penalties in the wake of the investigation.

Both sailing catamarans were subject to annual Coast Guard inspections because they sailed with six or more paying passengers. But the unauthorized modifications on the Na Hoku II were not found in an annual inspection, which is partially why the Coast Guard opted to examine its examination standards. The new standards include taking the mast off and performing a more thorough inspection of it.

The results of the investigations have been shared with the victims' families.

In both cases, the masts of the catamarans failed in strong winds.

The cases spurred the Coast Guard to look at commercial catamarans statewide.

In April and May 2007, Coast Guard inspectors boarded all 59 inspected sailing vessels in Hawaii to conduct examinations as a result of the two fatal cases. Of the 59 vessels inspected during that "surge operation," 11 vessels were found to have serious deficiencies that required action before the Coast Guard would approve the resumption of sail operations.