A rash of incidents involving envelopes containing a suspicious white powder had police scrambling around New York City on Monday and forced the nation's fourth-biggest bank, Wells Fargo & Company, to shut down five branches.     

In all six cases, the substance turned out to be "non- hazardous," and in one case, the powder was identified as corn starch, a police spokesman said.     

Four of the mailed envelopes contained an identical note, which included the language "Happy May Day," the spokesman said.     

The incident comes on the eve of a planned day of protests organised by the Occupy Wall Street movement and labour groups across the country. According to a website called maydaynyc.org, demonstrations are planned in New York City against "the corporations who rule our city."     

Ed Needham, a member of Occupy Wall Street's New York media team, said he had found no connection between the incident and his movement. "It doesn't sound like something that we would do," he said.     

A spokesman for Wells Fargo said its branches would remain closed pending further investigation by the police. The branch locations include Third Avenue and 47th Street; Madison Avenue and 34th Street; and Broadway and 85th Street.     

Since it was launched eight months ago, Occupy Wall Street has targeted US financial policies it blames for the yawning income gap between rich and poor - between what they called the 1 per cent and the 99 per cent.     

More than 500 protesters demonstrated at the bank's annual shareholder meeting in San Francisco last week to express anger over foreclosures, executive compensation and corporate taxes.      

Among other large banks, spokesmen for Bank of America Corporation and JPMorgan Chase & Company said they had not closed any branches on Monday due to suspicious envelopes. A Citigroup spokesman had no immediate comment.     

San Francisco-based Wells Fargo is the fourth-largest US bank by assets. – Reuters