Haitians displaced by Hurricane Matthew are living in "inhumane" conditions in government-run shelters, a United Nations expert said Tuesday.

The powerful storm crashed ashore in southwestern Haiti on October 4 packing winds of 145 miles (230 kilometers) per hour. At least 546 people were killed, and more than 175,000 people were displaced.

Three weeks after the storm, Gustavo Gallon, an independent UN human rights observer in Haiti, described his shock at the living conditions for storm refugees in shelters.

Gallon, who is wrapping up a nine-day tour of Haiti, visited Nord Alexis school, which is housing some 3,000 storm refugees, or 525 families, in the town of Jeremie.

They are surviving in "difficult conditions: no food, no access to health services, no drinking water, and without clean installations and proper toilets," Gallon said.

"These people are squeezed into 20 classrooms. They are hungry. There are two babies that were born there without help for delivery, and there are around 20 pregnant women there," said Colombian-born Gallon.

Warning of the psychological effects of the trauma, Gallon recalled how a young woman told him "we all became mentally ill."

"The conditions in which these people find themselves in are inhumane and should be resolved immediately," he added.

According to Haiti's Civil Protection service, the hurricane destroyed or heavily damaged more than 770 schools, and the schools that were unaffected have been taken over by thousands of displaced families.

Given the great stress suffered by storm refugees, many of whom lost everything, Gallon was perplexed by Haitian authorities' orders to prepare to resume classes.

Education officials notified the Nord Alexis school principal to prepare to restart classes in two weeks.

"He doesn't see how he can meet these demands," Gallon said.

Gallon is an independent expert who is not on the UN staff and "serves voluntarily and independently of any government or organization," according to his official biography.

He was appointed by the UN Human Rights Council to his post in June 2013, and has since visited Haiti six times.