CANBERRA (AP) — Australian authorities hold grave fears for 67 asylum seekers reported missing after they said they were leaving Indonesia in a rickety boat bound for Australia more than a month ago, an official said Tuesday.

The news comes as Australia's government debates a tough new bill aimed at deterring the flood of asylum seekers making the perilous sea journey.

Australian Customs and Border Protection Service were alerted over the weekend that the 67 had not been heard from since they told relatives that they would embark on the 400 kilometer (250 mile) voyage to the Australian Indian Ocean territory of Christmas Island in late June or early July, Home Affairs Minister Jason Clare said.

Customs had since checked a list of names of the missing against the hundreds of asylum seekers who had reached the island aboard overcrowded fishing boats in recent weeks, he said.

"There is no evidence that those people have arrived in Australia," Clare told reporters. "So we now have very grave fears for the safety of those people."

Earlier in June, more than 90 asylum seekers are believed to have drowned when two people smuggling boats capsized in the space of a week while attempting the same journey in rough seas. Another 240 were rescued and taken to a detention center on Christmas Island.