Navy-contracted divers have reattached more than 2,000 coral colonies that were displaced in February's grounding of a warship off Honolulu International Airport, officials said Friday.

Rear Adm. Joseph A. Walsh, deputy commander of the U.S. Pacific Fleet, said contractors were making steady progress collecting and reattaching the coral colonies.

The next phase of work will be the removal of rubble from the seabed.

The multimillion-dollar effort began April 29 to repair the environmental damage done to reef colonies dating back hundreds of years in the grounding area. The colonies provide shelter and feeding grounds for many different species.

The 9,600-ton USS Port Royal ran aground Feb. 5 about a half mile offshore. It sustained between $25 million and $40 million in damage while lodged atop the reef for four days in an area clearly marked on navigational charts.

The ship left a main gash through the reef covering about 1,600 square yards. The full extent was estimated to cover about 5,500 to 8,700 square yards.

Divers are working from a 74-foot-long former landing craft tethered to buoys. They're collecting colonies and fragments, then reattaching them to solid spots on the bottom with cement mortar.

Contractors have also been mobilizing equipment for the rubble removal, which the state said was critical to prevent further damage to the reef. The state is concerned that if left in place, the rubble could damage the reef when high surf hits the area.

Divers will place the rubble into loading nets by hand, and contractors will use hydraulic suction devices and an environmental cable arm bucket to remove coral and rock rubble and load it onto barges. Once ashore, the state will use it as fill material for the airport's Reef Runway.

Laura H. Thielen, chairwoman of the state Department of Land and Natural Resources, said the state appreciated the Navy's commitment to a timely response in regard to the removal of loose coral rubble, and is working together to ensure that further damage to the reef habitat is minimized.

Thielen said southerly summer swells could roll the rubble, possibly damaging the remaining reef. She said this gives added urgency to the task of removing the rubble.

Meanwhile, the Navy said its investigation into the cause of the grounding was continuing. The ship's commanding officer, Capt. John Carroll, was relieved of his duties in the meantime.