New information has delayed the re-entry plan for some neighbourhoods damaged by the Fort McMurray fire.

Premier Rachel Notley said in a news conference Monday that tests on ash, soil, air and water in some areas indicated “undamaged homes in certain areas are not immediately safe for re-occupation.”

“The ash has a very high pH,” said Alberta’s Chief Medical Officer of Health, Dr. Karen Grimsrud. “Which may cause both skin and respiratory irritation and burns.”

Grimsrud went on to note that heavy metals like arsenic were also present in the sample.

More than 500 homes were deemed unsafe, including 357 homes and 10 apartment complexes in Abasand, 27 homes and 1 apartment complex in Waterways and 183 homes and 1 apartment complex in Beacon Hill.

Residents of the area were scheduled to re-enter on June 4.

Though the homes are not safe to reside in, the province is working to arrange for people to temporarily return to inspect their homes and retrieve their belongings.

The majority of residents will be able to return as scheduled, beginning on Wednesday.