Problem with pointer deallocation in chained list

I have a problem with the deallocation of pointers in my code a few days ago. I try to make sure that the point of my on-screen object is greater than one value, move this object out of memory, but for some reason this is not working and is giving an error that hangs everything up.

Finally, I think I'm doing something very wrong, but I could not identify what it is, follow the code:

This is the structure I'm using for creating the list

//estruturas
//asteroide
struct Asteroides {
    int x;
    int y;
    int vel;
    ALLEGRO_BITMAP *Img;
    int id;
    char palavra;
};
//um tipo de variavel lista que eh um ponteiro
typedef struct elemento* Lista;
//define elemento
struct elemento {
    struct Asteroides dados;
    struct elemento *Prox;
};
//define um tipo de elemento auxiliar
typedef struct elemento Elem;

This is the allocation of the elements in the list:

//insere na lista
void ins_list(int num, Lista* li){
    srand(time(NULL));
    for(int i = 0; i < num; i++){
        Elem* no = (Elem*) malloc(sizeof(Elem));
        if(no == NULL) break;
        no->dados.Img = Asteroide;
        no->dados.x = (rand()%1000);
        no->dados.y = -200;
        no->dados.id = i;
        while(no->dados.vel <= 0 || no->dados.vel >5){
            no->dados.vel = (rand()%10);
        }
        no->Prox = (*li);
        *li = no;
    }
}

This is the part that I try to unsuccessfully remove, the removal code is along with the image refresh:

//anima asteroides
void anima(Lista* li, int frame, int agFramex, int agFramey){
    Elem* no = (Elem*) malloc(sizeof(Elem));
    Elem* ant = (Elem*) malloc(sizeof(Elem));
    no = (*li);
    ant = no;
    while(no != NULL){
        al_draw_bitmap_region(no->dados.Img, agFramex*frame, agFramey*frame, frame, frame, no->dados.x, no->dados.y, 0);
        if(no->dados.y > ALT+200){
            ant->Prox = no->Prox;
            free(no);
            no = ant->Prox;
        }
        no->dados.y += no->dados.vel;
        ant = no;
        no = no->Prox;
    }
}

If if is the removal code:

if(no->dados.y > ALT+200){
   ant->Prox = no->Prox;
   free(no);
   no = ant->Prox;
 }

I get segmentation fault 11 which is actually allocation error, can anyone help me? Thank you.

Obs: The error occurs when the first object reaches the condition.