Officials are working to clear the site of derailed train that leaked hazardous chemical materials and forced the evacuation of over 100 homes in the US state of Louisiana Monday.

Crews began replacing a stretch of the damaged rail track Monday afternoon, which is expected to complete late Monday or early Tuesday, Doug Cain, a spokesman for Louisiana State Police said.

Cleanup is also carried out on a highway that runs parallel to the track and was blocked by the accident. The highway would stay closed for at least two days.

Residents who have been evacuated from areas near the derailment still remained in hotels and were warned against returning their homes. It's unclear how long those families will be asked to remain out of their homes.

State Governor Bobby Jindal declared a state of emergency earlier Monday after hazardous leaks were confirmed.

The Governor's Office of Homeland Security and Emergency Preparedness said three cars were leaking. One car is leaking lubricant oil, a second is leaking a class 8 substance known as caustic soda and the third car is carrying a class 9 hazardous substance called Dodecanol.

The class labels are measured in terms of the materials' hazardous properties. Class 9, the highest, means miscellaneous dangerous goods while class 8 refers to corrosives.

The derailment happened late Sunday in Lawtell, about 100 km west of Louisiana's capital city Baton Rouge. At least 26 cars on the 76-car Union Pacific train went off the tracks. Two people were on the train, an engineer and a conductor, at the time of the accident. Neither was hurt.

Earlier reports said 14 of the 26 derailed cars contained "regulated substances" that are harmful or toxic. Union Pacific spokeswoman Raquel Espinoza told the media that two cars are leaking and one of them is leaking sodium hydroxide, which can cause injuries or even death if it is inhaled or touches the skin.

Cain, the police spokesman, said an inspection Monday showed the damaged train cars remained stable and the state Department of Environmental Quality has been monitoring the air but found no indication of any offsite impacts.

There is no final words on the severity of the leaks so far. Over 100 homes within 1.6 km of the derailment were evacuated Sunday as a precaution. The Governor's Office of Homeland Security and Emergency Preparedness said evacuation orders were still in place Monday.

It is not known what caused the derailment and an investigation is underway.