COLOMBO, June 23 (Xinhua) -- Sri Lankan defense authorities here Friday said that an investigation had been launched into a mysterious blast noise heard off the west coast.

    The residents at Uswatakeiyawa, 18 km north west of the capital Colombo reported hearing a huge blast off the seas around 10:00 a.m. local time (0430 GMT), the police said.

    The police chief Chandra Fernando said that it may have been a blast caused by a sea mine left behind by the Tamil Tigers on last Saturday.

    Several members of the Liberation Tigers of Tamil Eelam (LTTE) were arrested last Saturday when they had failed in an alleged mission to set bombs on several coastal guard boats.

    However, the Sri Lankan Air Force said the blast noise was caused by a sonic boom.

    Keheliya Rambukwella, the Minister of Policy Planning and the government's defense spokesman, said strict security measures have been put in place to prevent any terror attacks by the Tigers.

    Sri Lanka's Norwegian backed peace process aimed at ending the decades old separatist armed conflict is currently stalled due to an upsurge of violence blamed on both parties.

    Both sides say they remain committed to the Norwegian backed effort but accuses the other side of perpetrating violence. Enditem