JUYUAN, China - In a town where parents are grieving for the nearly 300 children killed when last month's earthquake toppled a middle school, a photograph hinting at shoddy school construction has disappeared from a public exhibition.

The image showed a hand clutching a twisted piece of steel rebar, no thicker than a pencil. The photo was taken at the ruins in Juyuan of a middle school, one of 40 that collapsed in the May 12 quake.

The photo was featured prominently among a collection of quake artifacts when it opened last week.

By the weekend, though, it was gone, an apparent indication of rising government sensitivity over the issue of shoddy school construction that has already prompted angry protests from parents of the dead children.

Exhibit organizers were reluctant to say exactly why it disappeared.

"We don't know if we were told to remove the photo," said Wu Zhiwei, assistant to the general manager of Museum Cluster Jianchuan, the organizer of the exhibit and the largest privately run museum in China.

"And if we were told to remove the photo, we're not sure we could tell you."

School collapses have become one of the most charged issues in the earthquake recovery process, and one that local communist leaders seem anxious to suppress.

The state-controlled media has largely ignored the issue, apparently under the propaganda bureau's instructions. Parents and volunteers who have questioned authorities have been detained and threatened.

Juyuan has become a center of the anger. Police have pulled grieving parents away from a courthouse where they knelt this month in an attempt to submit a lawsuit.

On Sunday, police cordoned off the area surrounding the town's collapsed middle school, angering parents who had come to observe the 35th day of mourning, a key date in local tradition.

"It's as if we're bad people now," said a man who said he was the father of a dead student.

"This is our last chance to burn incense and they don't let us in," said the man, who declined to give his name, underscoring a growing reluctance to be publicly identified and possibly targeted by authorities.

Engineers who inspected the school rubble say many of the facilities, including the one in Juyuan, were poorly sited and badly built.

The government promises a schools report by June 20, possibly opening the door to charges or lawsuits.

Authorities are always suspicious of independent activism, however, and the possibility of being implicated in school problems offers officials a strong incentive to suppress information about such cases.

Despite the removal of the photo from Juyuan, the quake exhibit on a sprawling campus about an hour's drive from the provincial capital of Chengdu still offered potent reminders of the tragedy.

There were schoolbook bags, smashed desks and children's shoes. These items sat alongside identification cards, crushed appliances and hundreds of photos of victims and relief workers.

The collection includes a megaphone said to have been used by Premier Wen Jiabao as he toured the ruins.

The exhibit ends with a wall of photos of about 2,000 people killed in the quake, China's worst natural disaster in a generation. In all, almost 70,000 people died.

Visitors on Saturday said they found the exhibit both open and moving.

"The earthquake isn't finished yet," said Zheng Chengzhi, a 42-year-old worker from Chengdu. "Construction and other issues, we need to talk about these things."