UPDATE: Officials probe new gas odours in city rocked by explosions

LAWRENCE, Mass. - A strong gas odour has brought officials back to one of the Massachusetts communities rocked just days ago by natural gas explosions and fires.

Firefighters and gas workers returned Saturday morning to a commercial area on the south side of Lawrence where they were seen opening manholes, testing gas levels and trying to gain access to businesses.

WCVB-TV reports the situation appeared to be contained by 11:15 a.m.

Officials, meanwhile, are also warning about donations scammers.

They say residents in Lawrence and Andover have received calls from individuals falsely claiming they're collecting donations on behalf of a local firefighter's association for the disaster.

A series of gas explosions Thursday killed a teenager, injured dozens, damaged homes and forced thousands of people to evacuate.

Meantime, a federal investigator now says there's no evidence to suggest the explosions were intentional.

National Transportation Safety Board Chairman Robert Sumwalt said Saturday as federal officials opened their investigation into Thursday's disaster that there doesn't appeal to be ``anything nefarious, anything suspicious, anything intentional.''

Sumwalt said it appears Columbia Gas' pipeline control centre in Columbus, Ohio registered a pressure increase in the Lawrence area.

He said investigators will be working to develop a timeline, including how local utility officials reacted to the pressure increase.

Investigators expect to be on site up to ten days. A final report could take up to two years.