Erika's father and younger sister appealed for her return
Detectives searching for missing girl Erika Kacicova say they believe the 13-year-old is alive.
Erika was last seen leaving her home in Darnall, Sheffield, at 16:00 BST on 5 August.
A 37-year-old man arrested earlier in Bradford on suspicion of child abduction had been in contact with her in the past four days, police said.
Det Insp Helen Tate, of South Yorkshire Police, has urged Erika to make contact.
She said: "The information we have is starting to knit together and I feel we are closing in.
"The arrest is most certainly a man that is known to Erika and I feel has had some contact with Erika over the last 48-96 hours.
Up to 50 officers are working on the case, South
Yorkshire Police said
"There have been sightings, albeit unconfirmed sightings, over the last 48 to 72 hours.
"When pieced together with other information it does lead me to believe that Erika is alive.
"There has been a lot of activity in the Bradford area and we've searched a number of addresses in the Bradford area."
'Bubbly and energetic'
The 37-year-old man is the second person to be arrested in connection with her disappearance.
A 22-year-old man arrested on suspicion of child abduction after handing himself in to police on Friday has been bailed.
Kelly Mills, a pastoral care worker at Erika's school in Sheffield, described Erika as "bubbly and energetic".
She said she and her colleagues were very worried and appealed for Erika to make contact with police.
"Erika, if you can hear this everyone at school is really, really, worried about you," she said.
"All we want to know is that you're safe. You are not in any trouble at all.
"If you can hear this please, please hand yourself over to the police."
Det Insp Tate said Erika had been missing before but it was out of character for her to disappear for so long.
The detective said Erika's family were "very distraught" and her younger brother and sister were "missing her terribly".
The force's search has centred on the Sheffield and Bradford areas where it is known the teenager has friends.
Erika is described as being about 4ft 11in (1.5m) tall, of slim build with long, dark brown, straight hair and brown eyes.
She was said to have been wearing dark blue jeans, and a denim short-sleeved top over a pink Adidas zip up hoodie when she left her Poole Road home in the Darnall area of the city.
The hoodie has yellow stripes down the arms and a white Adidas motif on the front. She was also wearing denim style ankle boots.
Erika speaks Slovakian and English with an eastern European accent, police said.
The man on bail is from Bradford and handed himself in to police on Friday.