Signs in opposition of technology companies are seen in San Francisco, California December 9, 2013. A Google Inc commuter bus was blocked in San Francisco's Mission district for about a half hour Monday morning, highlighting many residents' growing concern that an influx of affluent technology workers is driving up costs in the city. [Photo/Agencies]

SAN FRANCISCO - A Google Inc commuter bus was blocked in San Francisco's Mission district for about a half hour Monday morning, highlighting many residents'growing concern that an influx of affluent technology workers isdriving up costs in the city.

"San Francisco, not for sale" and "Stop evictions now" numbered among the slogans yellow-vested protesters chanted as they surrounded the double-decker bus. Google's offices are inMountain View, about 34 miles away from the incident.

The protest, organized by an advocacy group called Heart ofthe City, took aim at private commuter buses which whisk thousands of employees from stops around San Francisco to jobsat technology companies south of the city such as Apple Inc, Facebook Inc and Google.

Advocates of the buses say they ease traffic on already clogged highways as workers give up driving individual cars for the convenience of riding in the buses, which usually come with plush seats and WiFi.

Foes say the buses jam up municipal bus stops and remove potential customers from cash-strapped public transportationsystems, including regional rail service, that could use theirrevenue.

Google and the San Francisco Municipal Transportation Agencydid not immediately respond to requests for comment.

Bemused Google workers spent about a half hour sitting onthe bus until the protesters disbanded, many of the workerssending Tweets about the incident.

"My shuttle came under siege this morning," tweetedAlejandro Villarreal, who attached a photo of the scene as it appeared through the bus window. Villarreal's LinkedIn profile identifies him as a program manager at Google.

"Don't hate on me for my job," tweeted @FashionistaLab,whose Twitter description identifies her as a style editor at Google Shopping. "You think I LIKE commuting to Mountain View? This protest is dumb."

A man who screamed at protest organizer Erin McElroy, 31,was later identified as a union worker who was pretending to bea Google employee upset at being delayed by the protest.

Increasingly, graffiti has appeared around town complainingabout the buses.

"Google scum," read one notice pasted to a light controllerat the corner of South Van Ness Street, a major artery for thecommuter buses, photographed by local resident George Lipp onSunday. "Keep catching your bus," read a notice on the otherside of the light controller.

The commuter-bus situation "has become very symbolic of what's happening to the city in terms of gentrification," said McElroy in a phone interview. "It's creating a system where San Francisco is being flooded with capital, and creating a technology class where other people can't compete."

Heart of the City is planning a demonstration Tuesday against a developer that plans to evict residents from rent-controlled apartments, she added. The total number ofevictions jumped 25 percent to 1,716 in the 12 months ending in February 2013, according to a report by San Francisco's budgetand legislative analyst, despite strong tenant-protection laws.

San Francisco protests against gentrification and evictionshave occurred with growing frequency in recent months.

Last month, message service Twitter's IPO sparked ademonstration outside its headquarters. Many residents feel left out of the technology boom and blame it forrising rents.

The median rent on a two-bedroom apartment rose 10 percentover the last year to $3,250, more than any other city in thecountry, according to online real-estate company Trulia. Rentsin greater New York rose just 2.8 percent

The current situation evokes the late 1990s, when a slew ofsmall Web start-ups popped up throughout the city, causingtensions over rising rents and traffic.