An "electronic ping" was picked up from the Malaysia Airlines flight by satellites after the plane lost contact with ground control, Reuters reports. Meanwhile, US officials have been given an "indication" the plane crashed into the Indian Ocean.
Messages reading "Have Hope" have appeared in China and Malaysia as the search for flight MH370 enters its fourth day.
Students in Zhejiang province, China lit candles and held placards saying "Pray for life", while well-wishers signed a board at Kuala Lumpur International Airport.
Efforts to find the locate the plane, carrying 239 people, have so far failed and authorities have widened the search area.
A mother has described her frustration as she waits for answers on the fate of her missing son who is on board the missing Malaysia plane.
Malaysia's military believes a jetliner missing for almost four days turned and flew hundreds of kilometres to the west.
The wife of a passenger travelling on the missing Malaysia Airlines flight has spoken of her struggle to cope as she waits for news.