Investigators have said that structural weakness was probably to blame for the sinking of an oil tanker off the French coast in December.

The Erika sank in bad weather off Brittany, releasing oil which has caused serious pollution along France's Atlantic coast.

The French transport ministry report absolves the ship's crew of blame but accuses both the Erika's Italian owners and the company charged with monitoring its sea-worthiness of failing to register the possible problems.

It said that despite indications about the potential problems - most notably from the ship's crew - those responsible for the 25-year-old, Maltese-registered Erika failed to react.

The ship's Indian captain, Karun Mathur, has been placed under official investigation by magistrates on suspicion of endangering lives and breaching anti-pollution regulations.

But the report appears to absolve him, along with his 25-strong crew.

"It did what it could with the equipment it had at its disposal ... without doubt, any different action would not have changed the course of events," the report says.

All crew members were rescued when the Erika broke up in stormy seas on 12 December.

The tanker had been chartered by French oil firm TotalFina, which has come under criticism for using such an old vessel.

Environmentalists have called for new shipping regulations banning single-hull tankers like the Erika from being used in European waters.

The French Government has called for an urgent review of international shipping regulations in light of the disaster.

Slicks continue

Oil from the Erika's 25,000-tonne load is still coming ashore, affecting 400km (250 miles) of coastline, killing or injuring an estimated 300,000 sea birds.

Specialists and volunteers still face a huge task. But local officials say the beaches will be ready for this summer's tourist season.

The head of France's coastal authority, Francois Letourneux, said clean-up teams were using experience gained after the huge 1978 Amoco Cadiz oil spill off Britanny.

"We are better prepared technically" he said. "We won't be applying any brutal treatment that would cause more harm than good.

"We mustn't remove too much sand from the beaches by skimming the surface, or go over dunes with bulldozers," he said.

"We're better off having tidal flats with small patches of oil than no tidal flats at all."