Two women, one 76 years old, suffered life-threatening injuries when they were attacked during an apparent home invasion in San Francisco's Sunset District, police said Friday.

A 57-year-old woman, who neighbors said owns a nearby Chinese restaurant, was delivering food to the home of the older woman on the 1700 block of 20th Avenue near Noriega Street around 9:20 p.m. Thursday when she stumbled upon the apparent home invasion.

A man opened the front door, hit the woman numerous times in the head and fled in a light-colored, four-door sedan, police said. The woman stumbled back to the restaurant, leaving a trail of blood on the sidewalk, and called police.

When officers responded, they found the 76-year-old woman suffering from numerous stab wounds to her upper body and head trauma.

Both women were taken to hospitals and were listed in critical condition, police said. Their names have not been released.

No arrests have been made. Investigators do not have a motive for the attack but do not believe it was a burglary, said Officer Albie Esparza, a police spokesman.

Neighbors said the younger woman owns a Chinese restaurant at 1311 Noriega St. The restaurant, which usually opens at 11 a.m., was closed Friday, and employees inside were cleaning blood off the floor.

Blood was also spattered on the front steps to the house where the attack occurred, and was smeared on the doorknob area and one of the house's front walls.

David Smith, a 77-year-old barber who works on the block, was shocked to hear of the violence. He considers the area to be safe after working there for 20 years.

"This is unusual," he said. "It's usually very quiet."

Anyone with information on the attack is asked to call police at (415) 575-4444 or text information to TIP411, including the phrase SFPD.