GREENLAND - About a dozen fifth-graders at Greenland Central School complained of headaches and nausea around the same time Thursday morning, but fire officials said there were no signs of carbon monoxide or other gases in the air.

Greenland emergency crews were called to the school after the students fell ill around 9:30 a.m. and went to the nurse's office.

"We went in with gas meters and tested the air and we found nothing at all. It was all clear," Fire Chief Ralph Cresta said.

Emergency medical technicians examined the students, but all of their vital signs were normal, and none were transported to the hospital, Cresta said. The students were released to their parents.

The exact cause of the sickness wasn't determined, but Cresta said it may be a case of the flu and was coincidental that they all began feeling ill around the same time.

"This flu that's been going around has been pretty bad," Cresta said.

School superintendent George Cushing said he isn't aware of any science projects being done around the time the students began feeling sick.

Like at other schools, some Greenland students and staff have been hit with the influenza-like symptoms, including a fifth-grade teacher who recently returned to school after battling the flu, Cushing said.

One ambulance from Greenland responded to the school.

"We were just trying to get some support from the fire department and the EMTs to figure out what was going on," Cushing said.

In a letter to parents, school principal Peter Smith said the school's nurse reported the incident to the state's public health nurse.