I HAVE A PROBLEM WITH MY DAUGHTER AND NEED HELP ASAP!!!!!!!?

I have a wonderfull 11 year old daughter, well ima try to make this story short,,,ther is this grl (10yrs old) that my daughter likes, she lives down 1 block she also has a older bro and an older sis. i get along well with ther mom and them. there mom is an alcoholic and they are always home on ther own, in the care of there older bro that is, but they are like the troubled nieghborhood kids. they out after dark (9pm) all the time, cops are always at there house,and i was told that they curse, bully other kids and steel as well. I personally have never witness the curseing,steeling,and smokeing from them. but hearing these things concern me BADLY.. i realy dont like wen my daughter hangs with them.And i am always telling her no she cant go down there today, maybe the next day or something like that. but there are nice to me. i have this feeling though that they do, do bad things,,OR DO I just dont want to believe it??? when she asks why cant she hang with them everyday, i always say" because i have my reasons" i dont no how to explaine to my daughter why i realy dont care for them being around her. i cant proove to myself nor to them that they are bad. and i realy dont want to create any kinda war around here between mines and there kids..cuz you no that means bullying and teasing and tormenting and harassment will start to appear. its not fair to her how on how im feeling is it??? PLEASE can someone help me on how to take action and what do i do about this feeling that i have?