Three people have been injured in a shooting at a high school in Maryland, including the perpetrator, a sheriff’s spokeswoman said.

There were no fatalities in the shooting at Great Mills High School, St Mary’s County Sheriff’s spokeswoman Cpl Julie Yingling said.

Cpl Yingling said the two victims were shot, but she does not know how the shooter was injured.

The three injured were all taken to hospital.

The principal told parents last month that the school had investigated threats of a possible shooting and found they were “not substantiated”.

Jake Heibel told parents that school officials interviewed two students in February who were overheard mentioning a school shooting and found that they posed no threat.

His letter was posted on local news site The Bay Net.

But Mr Heibel said the school still increased its security after social media posts about a possible school shooting “circulated quite extensively”.