MEXICO CITY, June 3 (Reuters) - Biologists in Mexico plan to tag hundreds of sharks off the Pacific Coast to help understand the cause of a rare spate of deadly attacks on humans, the local government said on Tuesday.

Sharks near the southwestern resort of Ixtapa-Zihuatanejo killed two surfers and maimed another in the past few weeks, the first fatal shark attacks along Mexico's Pacific coast in 30 years, according to official records.

Biologists plan to tag sharks and ask fisherman to look out for them and report back on their movements, Guerrero state Environment Secretary Sabas Arturo de la Rosa told Reuters.

A smaller group of sharks will be tagged with electronic devices that would transmit data on their behavior and locations to biologists via radio frequencies, he said.

The tagging is expected to begin in about two months and the study should last a year.

"We need to get to the 'why' these animals are coming so close to Guerrero's shores, which is so unusual," De la Rosa said.

Shark experts believe unusually cool sea-surface temperatures could be partly responsible for the attacks, but they also note that a dearth of data about sharks in the region makes it difficult to reach conclusions.

The researchers plan to use a special baited fishing line to catch sharks in the area and then tag and release them, said Jose Leonardo Castillo, a shark expert with the National Fishing Institute who is involved with the project.

Fishermen who come across tagged sharks will be compensated for reporting their location, Castillo said.

More expensive telemetric tags on a smaller number of sharks will emit radio frequencies that scientists can track.

Surfer Bruce Grimes from Texas recently became the third person to be bitten by a shark since late April. Grimes survived the attack but needed 100 stitches in his arm. (Reporting by Mariano Castillo; Editing by Cynthia Osterman)

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