A mortar shell fired from Syria exploded in the Israeli-controlled Golan Heights on Wednesday, falling in an open area and causing no casualties, the Israeli military said.

Military officials said the shell landed near an Israeli village near the Syrian frontier. They said investigators were still trying to determine who fired the shell, and whether it was aimed toward Israel or was stray fire from the civil war in neighboring Syria. The officials spoke on condition of anonymity under military policy.

In recent months, stray fire from the fighting in Syria has occasionally landed in Israeli-controlled territory. On several occasions, Israel has returned fire. Israel did not respond to Thursday's shelling.

Israeli military officials fear the fighting in Syria could spill over into Israel. The Syrian military has fought rebels in the area near the frontier.

Earlier Wednesday, the military said six Syrians who were wounded in the fighting in Syria returned to their country after receiving medical treatment in Israel.

The military said the six had completed their treatment, and the military took them to an undisclosed location from where they returned to Syria on Wednesday. The military would not comment on why they were returned to Syria, where they could be in danger. It was not known if the Syrians requested to stay in Israel.

Two weeks ago, seven Syrian men approached the frontier between Syria and the Israeli-controlled Golan Heights. Israeli soldiers gave them first aid before transferring them to a hospital. It was the first time Syrians sought help in Israel during their civil war. The two countries regard each other as enemies.

The military said the seventh Syrian, who was severely wounded, remains in an Israeli hospital for further treatment.