The Coast Guard is investigating what caused a 734-foot merchant ship to run aground off Kalaeloa Barbers Point Harbor yesterday.

The Liberian-flagged VogeTrader became lodged on the reef in the entrance channel of the harbor at 7:25 a.m. The harbor pilot was on board the vessel as it was inbound when it went aground, the Coast Guard said.

Tugboats pulled the ship free at 2:50 p.m. Ballast was loaded to the left side of the ship to raise the right side to pull the vessel free.

Coast Guard spokesman Lt. John Titchen said no oil or fuel was released into the ocean. The VogeTrader, carrying coal, will be towed to an anchorage to repair a crack in the hull. A temporary patch will be used until it is determined where the merchant ship will go next for permanent repairs, Titchen said. An HH-65 helicopter was to monitor repairs yesterday.

Coast Guard Cmdr. Bob McFarland, acting captain of the Honolulu port, said the grounding did not seriously disrupt ship traffic.

The Department of Land and Natural Resources will send a biologist to the site sometime next week to investigate whether coral in the area was damaged by the vessel. The Coast Guard is confident the ship ran aground in the channel, Titchen said.

Meanwhile, the ship's crew will undergo drug and alcohol screening, a standard procedure in the investigation. The harbor pilot who was aboard the ship already underwent such tests at the Queen's Medical Center.

At this time last year, the 567-foot USS Port Royal ran aground off Honolulu Airport. It is also the same month when the 550-foot Hong Kong-flagged ship Cape Flattery ran aground outside the Barbers Point Harbor's entrance five years ago.

The USS Port Royal ran aground about a half-mile south of the airport on Feb. 5, 2009, while it was on its first day of sea trials. Divers determined the guided-missile cruiser damaged coral reef.

On Feb. 2, 2005, the Cape Flattery ran aground outside the Barbers Point Harbor entrance. The bulk cargo ship also damaged coral reef after it was grounded for nine days. Cement also spilled into the ocean as a crane and barge offloaded the cargo to help free the ship from the reef.