(Reuters) - Six months after Malaysia Airlines Flight MH370 went missing, relatives of those lost, desperate for any hint of what happened, say Chinese authorities have become openly hostile toward them.

In interviews, several relatives described how they had been detained and physically abused by police -- seemingly in retaliation for publicly pressing Chinese and Malaysia Airlines authorities for information about the hunt for the plane.

"In the beginning, Beijing police were protecting us, but their attitude has completely changed," said 38-year-old Cheng Liping, whose husband was on the flight.

"I can't fathom why they're doing this. I feel so incredibly disappointed."

The Boeing 777 aircraft carrying 239 passengers and crew, disappeared on March 8 after taking off from Malaysia's capital, Kuala Lumpur, bound for Beijing. About two thirds of those on board were from China.

Investigators say what little evidence they have to work with suggests the plane was deliberately diverted thousands of kilometers from its scheduled route before eventually plunging into the Indian Ocean.

But no one knows for sure, or why. A painstaking international search has failed to find any trace.

For the relatives, neither their pain nor their single-minded quest for answers has eased, and that seems to have become an annoyance for China's authorities.

Police have beaten at least two people whose children were on the flight, several family members said. In one case, a woman in her fifties was hospitalized for three days.

"I went to see her in hospital, I could see the injuries on her head and body," said Zhang Yongli, 64, whose daughter was on the flight. "The way the police acted was very extreme, it's wrong to treat us this way."

Beijing police did not respond to requests for comment.

China's government has repeatedly said it would spare no effort in the search for the plane and leaders have expressed sympathy for the families.

Public security authorities have not commented on the families but Malaysia Airlines representatives said distraught relatives have sometimes been aggressive.

Some relatives said they believed their homes were being watched. Police have detained people several times at an office the government has set up in a nondescript Beijing suburb where families can go to seek information about the search from Malaysia Airlines and government representatives.

Detentions usually last for about 24 hours, said the families and their lawyer. Police have cited various reasons for the detentions, family members said, including a rule against large gatherings. In a couple of cases, children were taken into custody with adult relatives.

In at least two other cases, recounted to Reuters by relatives, Beijing police went to family members' homes before dawn to detain them without a reason.

"On some level I can understand why the police are doing this - perhaps they're used to only dealing with bad people," said Liu Wanyi, 26, a newlywed whose husband was on the plane.

"But we're not seeking to antagonize the government in any way."



In the weeks after the flight disappeared, when media attention was intense, police were a constant presence at the Lido Hotel in Beijing, where Malaysia Airlines put up the families and held daily meetings.

At one demonstration in those early weeks, dozens of police escorted family members, many weeping and holding up signs, on a march to the Malaysian Embassy - an unusual show of support for a protest in China.

But as the story faded from the news and the search dragged on, authorities became less supportive, the families say.

Cheng, who has two young sons and who herself has been detained at the representative office, said she had no way to access her husband's Malaysian bank account, and authorities in both countries had been indifferent to her requests for help.

"Honestly, I can't endure this," she said. "My life has completely changed, I can't manage to work anymore."

Most family members visit the representative office at least once a week, some traveling for hours, they said, in the hope of a shred of information.

Like Cheng, many of them have quit their jobs.

Police treatment of the families mirrors that meted out to so-called petitioners, who seek redress for a range of perceived injustices such as land grabs and medical malpractice, which are common complaints in China.

Courts in China are controlled by the Communist Party and generally seen as beyond the reach of ordinary folk. With no other channels for pursuing complaints, people come to Beijing to make their cases but typically get short shrift.

Many are detained by police or forced back to their hometowns with no progress on their grievances.

As the flow of information from the search for MH370 dries up, relatives are haunted by their theories. Many said they believed the United States or other powers had withheld information or were even responsible.

"I have no doubt in my mind that Obama knows," Liu said of the U.S. president.

"No matter how much we ask, none of the responsible parties will provide any proof of what happened. Who knows what motive is behind it?"