VANCOUVER - Police in British Columbia have been told they don't have enough evidence to prosecute some of the smugglers who brought Chinese migrants to Canada last summer, CBC News has learned.

• INDEPTH: Chinese Immigration
  

• RELATED: Refugee hearings slated to start

The RCMP were hoping to lay human smuggling charges against the crew of the first boat that brought 125 people to B.C., but the Crown felt the charges wouldn't stand up in court.

The Crown has sent the file back to police and told them to keeping working on it.

"The fact that it's not approved at this point does not mean it won't be approved at some time," RCMP Cpl. Grant Learned told CBC News. "It just means that there's going to be additional work required and they don't have any idea how long that will take at this point."

Learned said the police investigations into the other three migrant ships that arrived later in the summer are still ongoing.

The 19 crew from boat one have claimed refugee status in Canada, as have the 67 passengers who remain in Canada.

Thirty-seven other migrants disappeared once they were released from custody.

In the past, police have said many Chinese migrants seemed to know little about the "snakeheads" -- gang members -- who brought them to Canada.