A security alert in the Springhill Park area of Strabane has ended and the remains of a viable device have been recovered.
Police said the alert began at 1130 BST following a report of a suspicious object.
It is believed the device was thrown during the night and exploded at the door of the house which was unoccupied at the time.
A number of families evacuated during the alert have returned to their homes.
The attack was condemned by PSNI area commander Chief Inspector Andy Lemon.
"This device could have caused serious harm or injury to any member of this community and this cannot be tolerated," he said.
"The entire community has been disrupted today and families have been forced to leave their homes. There is no place for attacks of this nature in our society."