PERTH, Australia, April 4 -- Chinese patrol ship Haixun 01 has intensified efforts to detect signals emitted from the black box of missing Malaysia Airlines Flight MH370 since Friday morning off the Australian western coast.

On Friday, Haixun 01 arrived at the new search area to the north of the 1.15 million square-kilometer patch earlier designated by Australia, according to a Xinhua reporter aboard the Chinese search vessel.

A shipboard rescue boat carrying a black box detector searched the area from 9:20 a.m. Beijing time (0120 GMT) until noon, with no significant findings. Haixun 01 also searched at dusk on Thursday.

The task is made tremendously difficult with no definite water zone and an increased water depth as the vessel moved north, said Zhang Liang, the survey captain from the Shanghai Maritime Center of Surveying and Mapping who is traveling with the rescue team.

The water depth at Haixun 01's current location is about 5,000 meters, according to Zhang.

Meanwhile, two ships equipped with pinger locators, sent by Australia and Britain respectively, commenced subsurface search for the MH370 black box, according to the Joint Agency Coordination Center (JACC), which coordinates the ongoing massive multinational search in the southern Indian Ocean.

The special devices can pick up signals sent out by black boxes, but the battery of the missing jet's black box is expected to expire in the coming few days.

"The area of highest probability as to where the aircraft might have entered the water is the area where the underwater search will commence," said Angus Houston, chief of the JACC.

"On best advice the locator beacon will last about a month before it ceases its transmissions. We're now getting pretty close to the time when it might expire," he noted.

The Australian Maritime Safety Authority has determined a search area of about 217,000 square kilometers, 1,700 kilometers north west of Perth.

Search teams spotted some objects on Friday, but none was related to the missing jetliner, the JACC said in a press release after a day's search.

"Today there have been some sightings of objects reported by ships in the search area but none were associated with MH370 (as at 1900 AEDT)," the JACC said.

A total of 10 military planes, four civil jets and nine ships are involved in Friday's search. Weather in the search area was good, with visibility greater than 10 km.

MH370 vanished on March 8 on its way from Kuala Lumpur to Beijing. The plane is believed to be lost in the Indian Ocean, claiming the lives of all 239 people on board, according to Malaysian authorities.