JERUSALEM (Reuters) - Israel's military on Tuesday closed an investigation into a 2009 shelling of a house in Gaza that killed 21 members of a Palestinian family, saying it did not constitute a war crime and that the civilians had not been targeted purposefully.
The incident occurred during a three-week war in the Hamas-ruled Gaza Strip.
Witnesses at the time said that on January 4, 2009 Israeli troops had ordered about 100 civilians in the Zeitun district to enter the house and stay there, out of their way.
But the following day the house was hit by Israeli shells and collapsed, killing the members of the extended Samouni family.
Reporting on Tuesday on the decision not to take legal action, Israel's Channel 10 television described the shelling as "the most serious operational mishap" of the Gaza war.
After an investigation into the shelling and allegations of war crimes, the Military Advocate General "found the accusations groundless", the military said in a statement.
"The Military Advocate General also found that none of the involved soldiers or officers acted in a negligent manner," the military said, but added it was making changes to "ensure that such events will not happen again".
Israel launched the offensive in late 2008 with the declared aim of ending cross-border rocket fire that continuously struck southern Israeli towns. Much of the fighting took place in densely populated areas of the small coastal territory. More than 1,400 Palestinians and 13 Israelis were killed.
A report released separately in 2009 by jurist Richard Goldstone under a mandate of the U.N. Human Rights Council said both Israel and the Islamist group Hamas were guilty of war crimes.
Israel refused to cooperate with the inquiry and strongly criticized Goldstone's conclusions as biased.
The Israeli group B'Tselem, one of the human rights groups that had submitted the complaint, said the response it received from the military did not detail the findings of the shelling investigation or provide reasons behind the decision to close the file.
"It is unacceptable that no one is found responsible for an action of the army that led to the killing of 21 uninvolved civilians, inside the building they entered under soldiers' orders, even if this was not done deliberately," Yael Stein, B'Tselem's head of research, said in a statement.
(Reporting by Ari Rabinovitch Editing by Maria Golovnina)