Police are investigating two attempted bank robberies that occurred in San Francisco on Friday afternoon, and are looking into whether they may have been committed by the same person, a police spokesman said Monday.

The first robbery attempt was reported at about 1:45 p.m. Friday in the 1200 block of Market Street, and the second happened about 20 minutes later in the 100 block of Pine Street.

In each case, the suspect approached a bank teller and handed over a note demanding money -- but when the teller walked away from the counter, the suspect fled, police said.

While the description of the suspect in the two robbery attempts varied slightly, in both cases he was described as a white man between 30 and 35 years old who is about 5 feet 4 or 5 inches tall and was wearing a striped hooded sweatshirt and Ugg-style boots, police spokesman Officer Albie Esparza said.

No weapon was seen in either robbery and no one was injured, Esparza said.

The incidents came on the heels of two bank robberies on Thursday -- one also in the 1200 block of Market Street and the other in the 200 block of Valencia Street.

Police believe both of those banks were robbed by the same person, described as a white man in his early to mid-30s -- but Esparza said he did not know whether Thursday's and Friday's robberies were connected.

Anyone with information about any of the cases is encouraged to call the Police Department's anonymous tip line at (415) 575-4444 or send a tip by text message to TIP411 with "SFPD" in the message.