POLICE were last night investigating whether a serious blaze at a company which has been the focus of illegal immigrant claims was started deliberately.

The fire at the Woo One factory, in Hartlepool, was tackled by 50 firefighters, who took more than two hours to bring it under control.

At its height, nine fire engines were at the scene and crews were called from all over Teesside.

Korean-owned Woo One, which supplies Samsung with plastic computer casings, was earlier this year subject to claims that it had been employing illegal immigrants from China.

It was then reportedly threatened with the loss of grants from regional development agency One NorthEast, should it have breached agreed conditions for the financial backing.

Last night, a police spokesman said the blaze in Brenda Road, Hartlepool, reported at about 8pm on Wednesday, was being treated as suspicious.

Firefighters had to search the factory after a security guard said he had seen someone on the premises.

Riasat Khaliq, group manager for Cleveland Fire Service, said the fire had begun in a storage area where plastic pellets used in the moulding process were kept.

He said: "Firefighters were met by quite an intense fire to the front of the factory.

"In the area where the fire was, the roof was severely damaged and part of it will have to be replaced."

The factory, which suffered 30 per cent fire damage, is understood to have closed earlier this week.

Woo One announced in February that it was laying off 68 workers, but said it hoped to win new contracts and resume trading later this year.

Four years ago, the company was paid £150,000 by One NorthEast on the proviso that it would diversify into microwave part manufacturing and create 75 jobs, although a further £100,000 in grants were withheld subject to further conditions.

A One NorthEast spokesman said: "We are monitoring the situation closely at the plant following the fire and can take steps to recover the RSA money at any time should we feel it necessary."

Calls to Woo One were last night being answered with the message that the telephone number was "temporarily out of order".

A spokesman for the Immigration Service said: "I can confirm that we are currently investigating illegal working activities in the North-East, but at this stage it would be inappropriate to comment further."