The search for evidence will continue on Saturday

Det Supt Mick Bradwell said he was following up leads in the Merseyside area after calls from the public.

The group of more than 30 cocklers were caught in rising tides on Thursday night; 16 are known to have survived.

Officers have begun interviewing some of the survivors, who are under social services care, through interpreters.

The incident has already sparked calls for more protection of migrant workers and strict licensing of cockle pickers.

'Dignity'

Assistant chief constable Julia Hodson, of Lancashire Police, told a news conference on Friday: "Nobody deserves to die in these circumstances."

She added: "We still do not know if the people involved are illegal workers, we still do not know if they had the required permits and if they were working for anyone else."

She said five of the survivors, who are all in the care of social services, were unknown to immigration service and four have since claimed political asylum.

The two non-Chinese survivors were described as white Europeans.

Morecambe Bay is a popular spot for cocklers

Cantonese and Mandarin translators are helping police to question survivors.

Police are also trying to identify the bodies and contact next of kin.

The Health and Safety Executive, the Chinese Embassy, the Coroner's Office and Lancashire County Council are also helping police.

A red pick-up truck containing bags of cockles was removed by police on Friday night, having been pulled from the sand at low tide.

'Gang master' register urged

Earlier on Friday, Ms Hodson said officers were considering the possibility of criminal charges.

She described gang bosses who profited from the slave labour of immigrants as "criminals of the worst possible kind".

Morecambe's deadly sands

On Saturday Don Pollard from the TGWU told BBC Radio 4's Today programme: "The big issue is the registration of gang masters.

"At the present time nothing is required of any gang master to register and that's what enables a lot of exploitation of workers to take place.

The Catholic bishop of Lancaster agreed, saying the government needed to address "rogue" gang masters in the UK.

Bishop Patrick O'Donoghue said: "I don't think that voluntary codes are sufficient here.

"I think we need the government to step in and set in legislation."

Huge rescue effort

The group of more than 30 cocklers were trapped by rising water in the Hest Bank area of the Lancashire bay.

They were pulled out of the near freezing sea during a huge rescue effort by coastguards, lifeboats and the RAF overnight.

Police say 17 of the dead are men while two are women. The 19th victim was recovered later on Friday afternoon.

The police in Lancashire are appealing for help in identifying the victims.