Zhang Jun, the girl's father, who works in Tianjin, strongly opposed the idea when the grandparents asked for his view. However, after lengthy attempts by the suspects to persuade the elderly couple, the grandmother finally gave her approval.

The pair promised to return with the girl the next day, but on July 5 and 6 they told the grandparents they could not obtain train tickets.

On July 7, the grandfather said they would contact police if they did not return. The mobile phone used by Liang and Xie was powered off, and the grandparents lost contact with them on that day.

The girl's father contacted Liang on July 4 after learning that the grandmother had given permission for the girl to go to Shanghai.

The father became suspicious when he found Liang had deleted his post on WeChat. When he messaged Liang to ask where they were, Liang initially said Xiamen in Fujian province. He then said they were in Ningbo, and then Wenzhou, both cities in Zhejiang.

Surveillance video shows Zhang Zixin appearing in a hotel doorway at a scenic spot in Xiangshan county, Ningbo, 300 kilometers southeast of Chun'an county, at 5:25 pm on July 7.

Early next day, Liang and Xie's bodies were found in Dongqian Lake, Ningbo. According to the Hangzhou newspaper Metropolitan Express, surveillance cameras showed the pair, tied together by clothing, walking peacefully toward a deep area of the lake.

Police later said the pair had been longtime "swindlers and transients" who had run out of money and decided they wanted to end their lives.

"A preliminary investigation found that they had, for some time, considered the idea of committing suicide, and had the motive and intention of seeking death along with that of the girl," a police spokesman said.

Liang and Xie had lived together since 2005 and had been cheating and borrowing money from friends and relatives for the past two years to pay for travel, police said.

Authorities in Zhejiang mobilized a team of more than 500 rescue workers using speedboats with sonar equipment in attempts to locate Zhang Zixin in caves on the coast, where she had last been seen.

Her body was found on Saturday in the sea off Xiangshan county, 30 km from where she had last been seen alive. An autopsy found she had drowned. There were no obvious injuries on her body, and police said they ruled out accidental drowning.