HOUSTON  State officials said late Friday that they had begun dismantling one of the largest dogfighting rings in the country that night, arresting eight people and seizing 187 dogs used by a sophisticated network of bettors throughout eastern Texas. Investigators continued to search for suspects Saturday.

In all, 55 people were indicted after an undercover investigation that lasted 17 months. Officials said the network’s matches drew crowds of up to 100 people, who placed tens of thousands of dollars in wagers on a single fight.

“This was a large-scale, highly organized operation,” said Lisa Block, a spokeswoman for the Texas Department of Public Safety.

It was not uncommon for a gambler to put $500 to $1,000 down on the matches, which took place weekly or twice a month at eight sites in secluded parts of Harris County, where Houston is the largest city, law enforcement officials said.