There have been protests in Mexico City over the disappearance of a 17-year-old university student, Marco Antonio Sanchez, after he was arrested by police on Tuesday.
Hundreds of people carrying placards called for his return on the city central avenue, stopping the traffic.
The student had been on the streets taking photographs but was arrested accused of stealing the camera.
Two of the policeman who took part in the arrest have now been detained.
Prayers were also heard for the missing student in the city’s cathedral.
Marco Antonio Sanchez’s family described him as a good boy who loved art and museums.
They said he had been out taking photographs when he asked another boy to use his camera to take a photograph of him by a wall which had interesting graffiti.
His friend said the police had come over and accused the youth of stealing the camera.
He had tried to run away but was caught and bundled into the back of a police van.
Mexico City government’s Human Rights Commission said it had demanded that the police investigate what had happened to the boy.
The commission said it has asked the city’s chief prosecutor to open an investigation into a forced disappearance.
Speaking at a press conference, a spokesman for the city police said the officers involved in the arrest had been questioned.
“They had released Marco Antonio after the arrest a few streets away because they had been asked to do so by local people in the area,” the spokesman said.
The police were examining video evidence and police radio traffic around the time of the arrest and were investigating what had happened to the youth, he added.
Police in several Mexican states have been accused of abuse, torture and extorting money from students and their families.
The most recent case to hit the news was the abuse and torture of seven students in Chilpancingo in Guerrero state.
The whereabouts of two of the seven is still unknown.