JackHammers, trucks, payloaders and the whine of saws rattled downtown New Bedford to life this morning as the city started to clean up after three gas explosions and fires yesterday. Three buildings were leveled and two more were heavily damaged.

Even as the cleanup continued, property owners, insurance companies, and city officials were busy assessing the damage and planning the rebuilding effort.

Fire Chief Manuel Almeida said the damage "could be in the millions of dollars.' But Ray Covill, of Humphrey, Covill and Coleman Insurance Agency, Inc., said that estimate may be on the high side.

"At this time it's too early to tell," Covill said.

Downtown merchants forced to evacuate an eight-block area yesterday because of high levels of gas were returning to their shops today. In many, broken windows were boarded up, but most had reopened for business.

Downtown businesses damaged by the blasts and fires were offered 30-day interest free loans this morning by Bay Bank Merchants of New Bedford as a "goodwill gesture and community concern effort" by the bank.

Mayor John A. Markey said today he will make federal Community Development funds available to businessmen for storefront renovations. Fifty per cent grants up to $2,00 will be offered.

Meanwhile, the New Bedford Gas and Edison Light Co. last night uncovered a crack in a 16-inch high-pressure gas main at Union Street and Johnny Cake Hill which they believe caused yesterday's devastation.

The crack was isolated at about 5 p.m. yesterday, and the gas fire which had raged for more than 12 hours was extinguished.

A spokesman for the state Department of Public Utilities said the department had an investigator on the scene yesterday and again today. A report will be issues later, he said. The cause of the bread was still unknown.

R. F. MacDonald, executive vice-president of the NBG&E, said the company is meeting with its insurance company today. He indicated the gas company may be liable for damage caused by the explosions.

Chief Almeida said the Fire Prevention Bureau is investigating the cause of the blasts and fires, but has not yet fixed the blame.

The Old Dartmouth Historical Society Whaling Museum was alive with activity this morning as contractors finished boarding up windows blown out by yesterday's blast.

The museum's treasures were unscathed, according to the museum Director Richard C. Kugler, and all but the Bourne Building, housing the half-scale whaling bark Lagoda, would reopen at about 10 a.m. tomorrow, he said.

Kugler said the museum has received calls from all over the country from people offering help and expressing concern about the museum's collection. Many had heard that the museum and nearby Seamen's Bethel were destroyed, he said. The fate of the museum-owned Whittle Building at 10 William St., heavily damaged in one of the gas explosions and fire at 7:08 yesterday morning, remained in doubt today.

Despite the hopes of the Waterfront Historic Area League that the early 19th-Century building be restored, Kugler said that the building was so Badly damaged "there seems to be no alternative to its demolition."