Vazquez was initially charged with "computer pornography/soliciting a child" and "providing obscene material to minors" by the Florida Department of Law Enforcement.
He was arraigned Tuesday afternoon in Pittsburgh and was denied bail, with the judge saying she was told that additional charges were expected.
Vazquez was subsequently charged in Westmoreland County, Pennsylvania, with three felonies -- statutory sexual assault of a minor 11 years or older; unlawful contact with a minor; and corruption of minors -- as well as one misdemeanor, indecent assault of a person less than 16 years old.
The FDLE issued a statement saying it began its investigation into Vazquez in August after obtaining information that he reportedly had a sexual relationship with a 13-year-old girl in Lee County, Florida. The girl, now 15, allegedly was continuing to have a relationship with Vazquez via text messaging and received a video from him in July in which he is shown performing a sex act, according to the police statement.
The police affidavit says the girl's mother found texts, photographs and the video sent by Vazquez to her daughter. On July 23, the mother "sent a text message, to include a screenshot of the photographs" to Vazquez to inform him that her daughter was a minor.
Vazquez has been put on administrative leave by Major League Baseball, though sources told ESPN that the league is not launching an immediate investigation because it plans to use the police's findings in pursuing potential discipline for Vazquez.
"Today we were made aware of an active law enforcement investigation involving Felipe Vazquez and his subsequent arrest," Pirates president Frank Coonelly said in a statement. "We take this matter, and these charges in particular, extremely seriously. We have informed the Commissioner's Office of the investigation and arrest.
"The Commissioner's Office will immediately place Felipe Vazquez on Administrative Leave (and, as a result, Restricted List) pursuant to the Joint MLB/MLBPA Policy. We need to be respectful to all involved and the ongoing legal proceeding. As a result, the organization, our staff and players cannot comment any further at this time."
The arrest was made by the FDLE with assistance from the Pennsylvania State Police. Several electronic devices were seized by police and will be examined as part of the investigation, with more charges possible for Vazquez.
The arrest warrant was issued in Lee County, Florida. Vazquez is in the Allegheny County Jail in Pittsburgh.
The administrative leave is pursuant to MLB's joint domestic violence, sexual assault and child abuse policy. A player can remain on leave up to seven days, but it can be extended if MLB and the MLB Players Association agree to it.
Pirates manager Clint Hurdle said he and team management met with players before Tuesday night's game against Seattle.
"We talked about a lot of different emotions that were stirred up today in a lot of different places," Hurdle said, "and how do we connect and support our way through those emotions. How do we continue to find ways to improve and hold ourselves to a high standard on and off the field. And what can we do from an organizational standpoint to help with any questions, any thoughts."
Vazquez, the Pirates' closer, is 5-1 with 28 saves, 90 strikeouts and a 1.65 ERA this season. He is a two-time All-Star selection and is signed with the Pirates through at least 2021.
Vazquez will be paid while on administrative leave, but the Pirates could attempt to void his contract. However, past efforts by teams to nullify deals, even in cases of illegal behavior, have proven difficult. He is owed $5.25 million for the 2020 season and $7.25 million for 2021. The Pirates also hold $10 million options on the 2022 and '23 seasons -- the first with a $1 million buyout and the second a $500,000 buyout.
Vazquez was among the most sought-after players before the July 31 trade deadline, with multiple teams pursuing him. The Pirates held out for an enormous asking price, valuing Vazquez -- and especially the four years of team control -- as one of the best assets in baseball. Teams found the Pirates' demands exorbitant, and Vazquez remained with Pittsburgh.
ESPN's Jeff Passan and The Associated Press contributed to this report.