Alex Smith’s 6-yard touchdown pass to Delanie Walker on fourth-and-goal with 1:51 remaining gave the San Francisco 49ers a 25-19 victory over host Detroit and handed the Lions their first loss of the season.

Frank Gore rushed for 141 yards and a touchdown, and the 49ers’ defense held the Lions (5-1) to 310 total yards – 69 below their season average – and snapped their nine-game winning streak.

San Francisco registered a safety when Aldon Smith sacked quarterback Matthew Stafford in the end zone and held Detroit to 66 yards rushing. The 49ers haven’t allowed a 100-yard rusher in 28 straight games, the longest active streak in the NFL.

Detroit turned it over on downs at its own 25 with 1:16 left and after San Francisco’s David Akers added a 37-yard field goal with 1:06 to go for the final points, the Lions gained only 11 yards on their last possession.

Niners coach Jim Harbaugh and Lions coach Jim Schwartz had to be separated following their postgame handshake.

The 49ers (5-1), who are off to their best start since 1998, trailed 10-0 before beginning their comeback with Gore’s 1-yard touchdown run on the first play of the second quarter.

Akers matched his season long with a 55-yard field goal on the final play of the first half to give the 49ers a 12-10 lead and put the Lions behind at halftime for the fourth straight game.

Stafford threw two touchdown passes, including a 5-yarder to Nate Burleson with 13:53 left to give Detroit a 19-15 lead.

Calvin Johnson caught his 300th career pass among his seven receptions for 113 yards, including his 10th touchdown of the season.

Green Bay, which defeated St. Louis 24-3 on Sunday, is the NFL’s only undefeated team.